docs: def resolution(self):
          """
          Get the tile resolution at the current position.
  
          The scale in WG84 depends on
              * the zoom level (obviously)
              * the latitude
              * the tile size
  
          References:
              * http://wiki.openstreetmap.org/wiki/Slippy_map_tilenames#Resolution_and_Scale
              * http://gis.stackexchange.com/questions/7430/what-ratio-scales-do-google-maps-zoom-levels-correspond-to
  
          Returns:
              float: meters per pixel
          """
          geo_coords = self.to_geographic()
          resolution = abs(_initialresolution * math.cos(geo_coords.lat * _pi_180) / (2**self.zoom))
          return resolution